Movement analysis of scoliotic subjects using Fastrak

An attempt has been made to simplify the measurement of composite movement involving abnormal rotation in scoliosis, which is considered to have an important role in the diagnosis and treatment of the condition. Analysis of three-dimensional movement provides pertinent information concerning the morphological description of scoliotic deformities. The description of this movement is of clinical interest for aiding diagnosis and/or prognosis of spinal deformity evolution. Previous studies have indicated that idiopathic scoliosis is a three-dimensional deformity accompanied by a generalised torsion phenomenon and attempts have been made to associate the geometric torsion index with the curvi-linear shape of idiopathic scoliosis. Although previous investigations have documented the three-dimensional reconstruction of scoliotic spine, most methods either expose the subject to a high level of radiation, as in stereo-radiographs, or demand a high degree of technical input and time, as in video based gait analysis systems. This study employs an electro magnetic field capturing system (FASTRAK) to estimate the spinal movements. This simple system is inexpensive and highly portable. Furthermore, it can give instant graphic and numerical values of the composite movement. The results of this study indicate the usefulness this system in the diagnosis of scoliosis and highlights the possibility of its uses in screening school children and other surveys.

Which central dual X-ray absorptiometry skeletal sites and regions of interest should be used to determine the diagnosis of osteoporosis?

Although central measurement of bone mass by dual X-ray absorptiometry (DXA) is viewed by many as the "gold standard" for the diagnosis of osteoporosis in patients without previous fragility fracture, controversy remains on how best to use central DXA as a tool for diagnosis. Questions concerning the measurement of bone mass of the central skeleton were addressed at the International Society for Clinical Densitometry Position Development Conference. An expert panel agreed on the following positions: First, the diagnosis of osteoporosis should be based on the lowest T-score of either the PA spine or hip. Second, both the PA spine and hip should be measured. Third, whenever possible, bone mineral density (BMD) of the first four lumbar vertebrae should be measured. Fourth, DXA manufacturers should use L1-L4 as the default region of interest for their printouts. Fifth, BMD of either hip may be measured. Sixth, the lowest T-score of the three sites total hip, femoral neck, or trochanter should be considered. Seventh, Ward's area should not be used for diagnostic purposes; DXA manufacturers should not include this region in the default printout. Eighth, BMD of the forearm should be measured if the hip or spine cannot be accurately measured. Finally, lateral spine BMD should not be used to diagnose osteoporosis.

Comparison of mechanical behaviour of normal and scoliotic vertebral segment: a preliminary numerical approach

Specific behaviour of the scoliotic spine has already been proven. The aim of this preliminary study is to evaluate if this behaviour is mainly due to geometrical deformities or to mechanical characteristics of soft tissues. We use a kriging technique to obtain a personalized finite element model of scoliotic spine from 3D reconstructions and from an existing detailed model of normal spine. To evaluate if deformed geometry has a share in specific behaviour of scoliotic spine, numerical simulations were performed on an apical segments extracted from normal and scoliotic models and the results were compared. Average mechanical properties of normal spine were considered in both models.

Spinal performance and functional impairment in postmenopausal women with osteoporosis and osteopenia without vertebral fracture

Previous studies have paid much attention to the impact on functional impairment or quality of life from vertebral fractures secondary to osteoporosis, but little research has addressed the function of osteoporotic women without fractures. The purposes of this study were: (1) to describe spinal performance and functional impairment in postmenopausal women with osteoporosis and osteopenia without vertebral fracture, and (2) to investigate the relationship between them. Thirty postmenopausal women diagnosed as having osteoporosis or osteopenia were recruited who fulfilled the following criteria: (1) menopause for at least 6 months; (2) no vertebral fracture; (3) no medication that would interfere with calcium intake. Measurements included assessment of functional impairment and spinal performance including trunk extension/flexion isokinetic strength, spinal range of motion (ROM) and movement velocity in three planes (sagittal, frontal and transverse). The results showed that spinal ROM and velocity were significantly reduced in the osteoporosis group compared with the osteopenia group ( p<0.05), but no significant difference in trunk strength was shown. Functional impairment level showed a slight difference between the two groups ( p = 0.042). There was a significant correlation between spinal ROM and motion velocity with bone mineral density; however, functional impairment correlated with motion velocity only in the transverse plane (trunk rotation) ( p<0.05). Spinal strength did not show any correlation with other parameters. It was concluded that spinal motion performance declined and functional impairment increased in relation to the severity of bone mineral loss in postmenopausal women without vertebral fracture, but their physical performance was not correlated with functional impairments.

How does neuropathophysiology affect the signs and symptoms of spinal disease?

A complex relationship exists between back pain and the presence of spinal disease. Particularly in chronic situations, back pain and its behavioural and emotional consequences are as likely to reflect the influence of psychosocial factors as any underlying spinal pathology. Nevertheless, physical factors are clearly important and it is significant that whereas in normal discs only the outer third of the annulus fibrosus is innervated, a much more extensive innervation develops in the presence of degeneration. Inflammation, as evidenced by leukocyte infiltration and expression of inflammatory mediators, is associated with disc degeneration and serves to alter the neural responses resulting in local and referred pain. It is probable that similar inflammatory processes, as well as direct root compression, contribute to radicular symptoms following disc herniation. An appreciation of these mechanisms encourages the search for novel treatments and permits a more rational and effective use of existing strategies for relieving pain.

Mechanical modulation of vertebral and tibial growth: diurnal versus full-time loading

The aim of this study was to determine whether the amount of growth response to mechanical compression and the underlying mechanism differed with night-time or day-time loading, relative to full time loading. Mechanical compression (nominally 0.1 MPa stress) was applied across tibial and tail vertebral growth plates of growing Sprague-Dawley rats. Four groups of animals were tested: 24/24 hour (full-time loading); 12/24 hour (day-loading); 12/24 hour (night-loading); and 0/24 hour (sham instrumented), 4 or 5 animals per group. After 8 days animals were euthanized and the growth plates were processed for quantitative histology of loaded and within-animal control growth plates to measure 24-hour growth, total and BrdU-positive proliferative zone chondrocyte counts, and hypertrophic chondrocyte enlargement in the growth direction.

RESULTS

Growth as a percentage of within-animal control averaged 82% (full-time); 93% (day-loading); 90% (night-loading); 100% (sham) for vertebrae. For proximal tibiae it averaged 70% (full-time); 84% (day-loading); 86% (night-loading); 89% (sham). Reduced amount of hypertrophic chondrocytic enlargement explained about half of this effect in full-time compressed growth plates, but was not significantly altered in half-time loaded growth plates. The remaining variation in growth was apparently explained by reduced total numbers of proliferative zone chondrocytes. The BrdU labeling index demonstrated an opposite trend, which was not statistically significant. In half-time loaded growth plates the proliferative zone cell count change predominated.

Spine loading characteristics of patients with low back pain compared with asymptomatic individuals

STUDY DESIGN

Patients with low back pain and asymptomatic individuals were evaluated while performing controlled and free-dynamic lifting tasks in a laboratory setting.

OBJECTIVE

To evaluate how low back pain influences spine loading during lifting tasks.

SUMMARY OF BACKGROUND DATA

An important, yet unresolved, issue associated with low back pain is whether patients with low back pain experience spine loading that differs from that of individuals who are asymptomatic for low back pain. This is important to understand because excessive spine loading is suspected of accelerating disc degeneration in those whose spines are damaged already.

METHODS

In this study, 22 patients with low back pain and 22 asymptomatic individuals performed controlled and free-dynamic exertions. Trunk muscle activity, trunk kinematics, and trunk kinetics were used to evaluate three- dimensional spine loading using an electromyography- assisted model in conjunction with a new electromyographic calibration procedure.

RESULTS

Patients with low back pain experienced 26% greater spine compression and 75% greater lateral shear (normalized to moment) than the asymptomatic group during the controlled exertions. The increased spine loading resulted from muscle coactivation. When permitted to move freely, the patients with low back pain compensated kinematically in an attempt to minimize external moment exposure. Increased muscle coactivation and greater body mass resulted in significantly increased absolute spine loading for the patients with low back pain, especially when lifting from low vertical heights.

CONCLUSIONS

The findings suggest a significant mechanical spine loading cost is associated with low back pain resulting from trunk muscle coactivation. This loading is further exacerbated by the increases in body weight that often accompany low back pain. Patient weight control and proper workplace design can minimize the additional spine loading associated with low back pain.

Relevance of Cobb method in progressing sagittal plane spinal deformity

Non-traumatic, progressing sagittal plane deformities are uncommon, but can lead to neurological deficit if untreated. The currently used Cobb method in assessing sagittal spinal curves is based on measuring the tilt of the end vertebrae. This study describes a method which quantifies the apex of the sagittal curve based on the apical quality as measured by the radius of curvature. Both this and the Cobb methods are compared to determine which has relevance in determining neurological deficit. Radiographs of 36 consecutive patients diagnosed with congenital kyphosis were reviewed. Twenty-four had normal neurology and 12 had neurological deficit as a result of sagittal curve progression. Both groups of patients had their weight bearing lateral radiographs analysed to measure the sagittal curve by the usual Cobb method and the Radius of Curvature method. There was no difference for the Cobb values for negative neurology and patients with positive neurological deficit (p = 0.3). There was a difference in these two groups when the radius of curvature method was used (p < 0.0005). The Radius of Curvature method has more relevance than Cobb method in quantifying sagittal plane deformity in congenital kyphosis when assessing neurological deficit.

Premature vertebral endplate ossification and mild disc degeneration in mice after inactivation of one allele belonging to the Col2a1 gene for Type II collagen

STUDY DESIGN

Skeletal tissues of mice with an inactivated allele of the Col2a1 gene for Type II collagen ("heterozygous knockout") were studied.

OBJECTIVE

To determine whether a heterozygous inactivation of the Col2a1 gene has a role in the etiology of spine disorders such as disc degeneration.

SUMMARY OF BACKGROUND DATA

Mutations in the COL2A1, COL11A1, COL11A2, and COL9A2 genes have been linked to spine disorders. However, the mechanism by which genetic factors lead to disc degeneration still are largely unknown.

METHODS

Spine tissues were studied using radiograph analyses; conventional, quantitative, and polarized light microscopy; immunohistochemistry for the major extracellular components, and in situ hybridization for procollagens alpha1(I) and alpha1(II). Voluntary running activity also was monitored in half of the mice.

RESULTS

As the findings showed, 1-month-old heterozygous knockout mice had shorter limb bones, skulls, and spines, as well as thicker and more irregular vertebral endplates, which calcified earlier than in the control mice. They also had a lower concentration of glycosaminoglycans in the anulus fibrosus, in the endplates, and in the vertebral bone than the controls. These features in the heterozygous knockout mice were compensated by the age of 15 months. However, the long bones and skulls of the mature heterozygous mice remained shorter than those of the controls. Gene-deficient mice used the running wheel less. However, physical exercise did not induce any marked structural changes in the skeleton.

CONCLUSION

Mice with heterozygous knockout of Col2a1 show subtle early skeletal manifestations that bear some resemblance to those of human spine disorders.

[The biomechanics of kyphosis]

Kyphosis is a dorsally convex curvature of the spine in the sagittal plane. A pathological kyphosis of the thoracic spine has a Cobb angle greater than 50 degrees. It occurs when the anterior and/or posterior load-transferring elements of the spine are overloaded or damaged. Wedge-shaped vertebral bodies may be found at one or several levels. A wedge-shaped vertebral body increases the curvature of the spine and moves the centre of gravity of the body parts above of the corresponding vertebral body in a ventral direction. This increases the flexion-bending moment acting on the spine. In the case of a wedge-shaped deformation of a vertebral body, the relative increase of the flexion moment is a function of the wedge angle and of the original position of the centre of gravity of the upper body.

Mechanical and pathologic consequences of induced concentric anular tears in an ovine model

STUDY DESIGN

Relations between induced concentric tears in the sheep disc and the mechanics of the intervertebral joint and vertebral body bone were analyzed.

OBJECTIVE

To examine the effect of concentric disc tears on the mechanics of the spine.

SUMMARY OF BACKGROUND DATA

Degeneration of the intervertebral disc results in changes to the mechanics and morphology of the spine, but the effect of concentric disc tears is unknown.

METHODS

In this study, 48 merino wethers were subjected to surgery, and discs were randomly selected for either a needlestick injury or induction of a concentric tear in the anterior and left anterolateral anulus. Sheep were randomly assigned to groups for killing at 0, 1, 3, 6, 12, and 18 months. From each sheep, two spine segments were mechanically tested: one with a needlestick injury and one with a concentric tear. Macroscopic disc morphology was assessed by three axial slices of the disc. Sagittal bone slices were taken from cranial and caudal vertebral bodies for histologic analysis.

RESULTS

Induced concentric tears decrease the stiffness of intact spine segments in left bending and the disc alone in flexion. In all other mechanical tests, the needlestick injury had the same effect as the induced concentric tear. In the isolated disc, the disc stiffness at 6 months was increased for right bending, as compared with the response at 1 month. This was associated with increased anterior lamellar thickening and increased vertebral body bone volume fraction.

CONCLUSIONS

Concentric tears and needlestick injury in the anterior anulus lead to mechanical changes in the disc and both anular lamellar thickness and vertebral body bone volume fraction. A needlestick injury through the anulus parallel to the lamellae produces progressive damage.

[Analysis of the changes of temporomandibular joint under repeated +Gz stress]

Changes of temporomandibular joint (TMJ) under repeated +Gz stress were discussed. From the etiological point of view in TMJ, many papers in the fields of aviation medicine, microcirculation, maxillofacial surgery and bone surgery were reviewed. +Gz forces can cause inadequacy of blood of oxygen supply to TMJ area. This situation can be worsened by release of free radical agent and cellular factors, ischemia/reperfusion injury, and/or hemorrheologic changes. Furthermore, G-induced injury of cervical muscles and spine may break the maxillofacial muscle chain balance. In addition to the above factors, mental stress may do harm to TMJ. This paper introduced the researches on this area in an attempt to enlighten the concern about TMJ responses to increased +Gz acceleration forces.

Misdiagnosis in vertebral osteomyelitis: problems and factors

One hundred and one cases diagnosed with vertebral osteomyelitis were evaluated for misdiagnosis and both factors and outcomes of misdiagnosis were assessed. There were 67 patients with tuberculous spondylitis and 34 patients with pyogenic vertebral osteomyelitis. Misdiagnosis occurred in 33.7 per cent of the cases. The average delayed diagnosis time was 2.6 months (range, 0.2 to 12). Age between 60 to 70 years was the most frequent group for misdiagnosis, while the most frequent area of misdiagnosis was the lumbar spine. Metastatic carcinoma, spinal stenosis, herniated nucleus palposus and back strain were common initial misdiagnoses. The factors, age group, absence of fever and positive straight leg raising test (SLRT) were associated with misdiagnosis in univariate analysis and multivariate analysis (odds ratio 3.40 (95%CI:1.07-11.94), 3.47 (95%CI:1.20-10.05), and 24.47 (95%CI:2.18-274.28), respectively) Misdiagnosis was statistically significantly associated with the result of treatment. This paper emphasizes that the elderly age group, absence of fever and positive SLRT are the independent factors which increase the risk of misdiagnosis of vertebral osteomyelitis.

Design of thoracolumbosacral orthosis (TLSO) braces using CT/MR

The field of orthotics has gained scientific attention over the last few years. Its objective is to correct, adjust, or modify the operation of human limbs, joints, or muscles. Thoracolumbosacral orthosis (TLSO) braces are used by scoliosis and postoperative patients who need back correction and/or support. The anatomic dimensions for TLSO braces have been acquired mainly by casting the patient. Casting is a time-proven method for obtaining surface geometry, but it can be inconvenient in certain situations. For example, casting might not be suitable for postoperative and trauma patients owing to the risk of further injury. Such prohibitive cases can still be handled safely by X-ray CT or MR scanning. This article presents an alternative method for data acquisition of TLSO patients' anatomic dimensions using CT/MRI. The experimental results show the method to be statistically accurate, efficient, and feasible compared with the conventional casting method.

Validity, reliability, and responsiveness of the fingertip-to-floor test

OBJECTIVE

To evaluate the validity, reliability, and responsiveness of the fingertip-to-floor test to assess total mobility when bending forward in standing position.

DESIGN

Experimental, prospective, correlational.

SETTING

Rehabilitation and radiology departments in a university hospital in France.

PARTICIPANTS

Ten patients (6 women, 4 men; mean age, 42yr) with chronic low back pain (LBP) in the validity study; 32 LBP patients (16 women, 16 men; mean age, 52yr) in the reliability study; and 72 LBP patients (22 women, 50 men; mean age, 30yr) in the responsiveness study.

INTERVENTIONS

Dynamic radiographs and fingertip-to-floor test.

MAIN OUTCOME MEASURES

For the validity study, 2 lateral radiographs of the upper dorsal spine, 1 in neutral position, and then 1 in full trunk flexion, were made. Validity was assessed by means of Spearman's correlation coefficient. Reliability was studied by using intraclass correlation coefficient (ICC) and the Bland and Altman method. Responsiveness was assessed by the effect size and the standardized response mean (SRM).

RESULTS

The Spearman's correlation coefficient for trunk flexion assessed by the test and the radiologic measure was excellent (r(s) = -.96). The intra- and interobserver reliability were excellent (ICC = .99). The Bland and Altman method showed no systematic trend. The values observed for the test were .97 for SRM and .87 for effect size.

CONCLUSIONS

Because the fingertip-to-floor test has excellent validity, reliability, and responsiveness, it can be used in clinical practice and therapeutic trials.

Factors that influence outcome in bracing large curves in patients with adolescent idiopathic scoliosis

STUDY DESIGN

A retrospective review of 51 patients with adolescent idiopathic scoliosis (AIS) treated with a Boston brace for curves ranging from 36 degrees to 45 degrees.

OBJECTIVES

To determine what radiographic or clinical observations may be predictive of outcome.

SUMMARY OF BACKGROUND DATA

Patients with AIS who are braced for curves >35 degrees are less likely to respond to conservative treatment than patients of similar maturity with smaller curves.

METHODS

Skeletally immature patients with AIS with no history of prior treatment were treated with a Boston brace. Cobb angles, vertebral tilt angles, coronal decompensation, apical vertebral translation(s), apical vertebral rotation, lateral trunk shift, rib vertebral angle difference, pelvic tilt, and the lumbar pelvic relationship (LPR) were measured at brace prescription, initial in-brace, brace discontinuation, and follow-up.

RESULTS

At the time of brace discontinuation, 31 patients (61%) were judged treatment successes. With follow-up observation, an additional eight patients progressed beyond 5 degrees, and a total of 16 patients (31%) required surgical correction. Only patients with double curves were found to have radiographic values predictive of outcome. The LPR angle, the association between the thoracic curve vertebral tilt angles and the amount of in-brace correction of the Cobb angle, were significant predictors. A patient's reported wear schedule significantly influenced outcome.

CONCLUSIONS

Patients with a double curve pattern in which the thoracic curve is >35 degrees and the LPR angle is >12 degrees are significantly more likely to demonstrate curve progression. In-brace correction for double curves of at least 25% and a patient's ability to wear the orthosis >18 hours/day significantly increased the likelihood of success.

Trabecular shear stress in human vertebral cancellous bone: intra- and inter-individual variations

Correlation of the mean and standard deviation of trabecular stresses has been proposed as a mechanism by which a strong relationship between the apparent strength and stiffness of cancellous bone can be achieved. The current study examined whether the relationship between the mean and standard deviation of trabecular von Mises stresses can be generalized for any group of cancellous bone. Cylindrical human vertebral cancellous bone specimens were cut in the infero-superior direction from T12 of 23 individuals (inter-individual group). Thirty nine additional specimens were prepared similarly from the T4-T12 and L2-L5 vertebrae of a 63 year old male (intra-individual group). The specimens were scanned by micro-computed tomography (microCT) and trabecular von Mises stresses were calculated using finite element modeling. The expected value, standard deviation and coefficient of variation of the von Mises stress were calculated form a three-parameter Weibull function fitted to von Mises stress data from each specimen. It was found that the average and standard deviation of trabecular von Mises shear stress were: (i) correlated with each other, supporting the idea that high correlation between the apparent strength and stiffness of cancellous bone can be achieved through controlling the trabecular level shear stress variations, (ii) dependent on anatomical site and sample group, suggesting that the variation of stresses are correlated to the mean stress to different degrees between vertebrae and individuals, and (iii) dependent on bone volume fraction, consistent with the idea that shear stress is less well controlled in bones with low BV/TV. The conversion of infero-superior loading into trabecular von Mises stresses was maximum for the tissue at the junction of the thoracic and lumbar spine (T12-L1) consistent with this junction being a common site of vertebral fracture.

Verbal categories for classification of spinal postures and their respective angular values registered by photographs and electrogoniometry

The perception of posture may allow workers to discern sensations associated with physical overload and potential tissue damage. In an occupational context, the classification of body postures in ranges of amplitude has been useful for researchers and ergonomists interested in evaluating the exposure of workers to uncomfortable and potentially harmful postures. In this paper we describe measurements, using photographs and electrogoniometry of the angle of flexion of the trunk and of the thoracolumbar segment, respectively, adopted according to the verbal categories of mild, moderate, and severe flexion, as requested by the experimenter. The results showed no differences between the groups of subjects, but significant differences occurred in the classification of the movement amplitude per verbal categories.

Plaster of Paris as bone substitute in spinal surgery

In order to assess the effectiveness of calcium sulphate (plaster of Paris; POP) as a substitute for autologous bone graft, we performed lumbar intervertebral fusion in mature sheep using POP and a variety of other graft materials, and reviewed the literature. The osteoconductivity of the POP grafts was compared to that of grafts carried out with autogenous iliac crest, frozen allogeneic bone, and ProOsteon 500 coralline bone. We also compared the osteogenicity of POP to admixtures of autogenous iliac crest bone with POP and coralline bone, and to an osteoinductive demineralized sheep bone preparation (DBM). The substrates were loaded into tubular titanium mesh, implanted into excavated disc spaces and recovered after a period of 4 months. Fusion mass segments tested in flexion and tension showed that POP was equal to autogenous bone and most other substrates. The POP fusions were significantly tougher than the DBM fusions, even though histomorphometry failed to reveal differences in the amount of trabecular bone. We conclude that POP can be used to achieve a biomechanically stable interbody lumbar vertebral fusion. In addition, our literature review indicated that POP can be used as a vehicle for local delivery of antibiotics in bone infections.

Vertebral reconstruction with cortical allograft: long-term evaluation

Reconstruction of large anterior vertebral column defects is indicated in a number of pathological conditions including tumor, infection, trauma and post-traumatic deformity. Several substitutes and techniques are available for the functional restoration of the vertebral column. Vascularized bone transfers, autografts, allografts or xenografts have been used, as well as metal or ceramic implants. All of these bear potential advantages and drawbacks in terms of associated morbidity of graft harvesting, disease transmission, mechanical failure, implant incorporation and overall long-term clinical outcome. In the present paper we report our experience with the use of freeze-dried, gamma-irradiated, cortical allograft for the reconstruction of large, anterior segmental defects of the spine, involving at least one vertebral body with its two adjacent discs. Cortical allografts were used in 67 cases operated for a variety of conditions. No case of disease transmission, infection or long-term mechanical graft failure occurred in our entire series, with a mean follow-up of 31 months. Fusion and mechanical stability was reliably obtained. Specific advantages include the absence of donor site morbidity, the possibilities for exact trimming to the size of the defect, superior mechanical strength as compared to available autograft, and reliable fusion with the host bone with partial bone remodeling, preventing fatigue failure. We conclude that freeze-dried, irradiated cortical allografts are safe and effective for anterior reconstruction of the spine.

The use of plate fixation in anterior surgery of the degenerative cervical spine: a comparative prospective clinical study

The method of anterior mono- or bisegmental cervical spine fusion is a well-established procedure for degenerative conditions of the cervical spine. While the early reports promote fusion with bone graft alone, recent studies report superior results with the addition of anterior plating. The objective of this study was to evaluate the influence of using plates in anterior cervical spine fusion in a prospective study. Fifty candidates for anterior monoor bisegmental cervical spine fusion were randomly and prospectively selected and assigned to a plated and a non-plated group. After a minimum follow-up of 22 months, patients were clinically and radiologically examined. The reduction in pain, improvement in neurology and functional assessment showed a significant improvement in both groups compared to the preoperative values. The total neurological score improved significantly in both groups, but the changes were greater in the group with plates. There was no significant difference between the groups for fusion rating, but graft quality (graft height) was significantly better in the plated group. We conclude that the overall data do not suggest better results with plating in mono- or bisegmental anterior spine fusions. Indications for additional internal fixation are restricted to special conditions with increased instability, insufficient bone quality or inappropriate graft placing.

Porous tricalcium phosphate and transforming growth factor used for anterior spine surgery

Harvesting autologous bone graft from the iliac crest is associated with considerable secondary morbidity. Bone graft substitutes such as porous ceramics are increasingly used for spinal surgery. This paper presents the results of an animal study in which beta-tricalcium phosphate (beta-TCP) bone substitutes were used for anterior spinal surgery in sheep and baboons. The presented baboon study also investigated the effect of impregnating the ceramic material with transforming growth factor (TGF). In the first study, using the sheep model, a stand-alone instrumented anterior fusion was performed. The animals were randomized into three treatment groups: autologous bone, beta-TCP granules, and sham group. The results were analyzed biomechanically and histologically at three survival intervals: 8, 16 and 32 weeks. An additional animal group was added later, with ceramic pre-filled implants. In the second study, a baboon model was used to assess the osteointegration of a 15-mm-diameter porous beta-TCP block into the vertebral body. The experiment was partially motivated by a new surgical procedure proposed for local bone graft harvest. Three treatment groups were used: beta-TCP plug, beta-TCP plug impregnated with TGF-beta3, and a sham group with empty defect. The evaluation for all animals included computer tomograms at 3 and 6 months, as well as histology at 6 months. In the sheep model, the mechanical evaluation failed to demonstrate differences between treatment groups. This was because massive anterior bone bridges formed in almost all the animals, masking the effects of individual treatments. Histologically, beta-TCP was shown to be a good osteoconductor. While multiple signs of implant micromotion were documented, pre-filling the cages markedly improved the histological fusion outcomes. In the baboon study, the beta-TCP plugs were completely osteointegrated at 6 months. For the group that used ceramic plugs impregnated with TGF-beta3, no incremental advantage was seen as a result of this particular application. However, TGF-beta3 is a potent growth factor at a very low dose. Not only does it speed up the ceramic material resorption, but it is also responsible for massive regional new bone formation. More experiments are required to better understand the biological effects of this growth factor in relation to bone formation, and to be able to take clinical advantage of them.